Valve operating mechanism



Sept. 12, 1933. A. NUTT El AL 1,926,349

VALVE OPERATING MECHANISM Filed Se t. 30. 1930 INVENTORS flRTHuR NUTT 0R THUR H. LEfi/f By HA per L. CHISHQLMJQ.

Patented Se t..12, 1933 t I 1,926,349

1,926,349 VALVE OPERATING MECHANISM Arthur Nutt, Eggertsville, Arthur H. Leak, Hamburg, and Barry L. Chisholm, In, Buffalo, N. Y., assignors to Curtiss Aeroplane & Motor Company, Inc., a corporation or NewYork Application September 30, 1930 Serial No. 485,408

16 Claims. (Cl. 123-55) Our invention relates to improvements'in valve same stroke, the described changes in the usual operating mechanisms for radial internal comvalve gear effect an identical timing in all cylbustion engines, and is especially adapted for inders and thus smooth out the exhaust noise engines used in aeronautics. and engine vibration.

In engines of this type there is usually a prin- In the drawing, in which like parts are repreo cipal or master connecting rod to which the sented by like numerals:

crankshaft ends of the other rods are articulat- Fig. 1 shows the master rod 4 with its circular ed. As a consequence of this construction the crankpin path 5 and the elliptical paths 6 and pistons of the articulated rods do not travel with 7 of the pins of the articulated rods 17 and 18;

10 the same speed at given points of the respective Fig. 2 shows the type of cam used with the 05 strokes as the piston of the master ,rod or of ofiset cam followers; each other. Similarly, a valve voperating mecha- Fig. 3 shows the center lines 13 of the usual nism arranged 'with equally spaced cams and cam followers and the center lines 14 of the followers," operating the usual push rods, will; offset cam followers, (dotted); and

15 not cause the valves associated, with the pistons Fig. 4 is a sectional view of the motor shown 70 of the articulated rods to open and close at the in Fig. 1 taken to show the cam and the cam folsame relative points ofthe piston strokes as the lowers by which the valves are actuated. opening and closing points of the valves asso- In Fig. 1-1, 2 and 3 are the cylinders of a ciated with the piston of the master rod. These three cylinder radial engine. 4 is the master differences are due to the crankshaft end of the connecting rod and 17 and 18 the articulated 75 master rod describing a circle while the crankrods. 8 is the crankshaft. 5 is the circular path shaft ends of the articulated rods describe irf th t r od in and 6 and '7 are the gu e ese ost noticeable effects o elliptical paths of the pins of the articulated this lack of piston phase symmetry are an ird r gula d d se d t ust ise and vi ra- In cylindersz and 3 the lines 10. 10 show the so .tionof the position of the piston when the exhaust valve One object .of this inventionis to correct the creeks o using th us al type of valve gear. above defects. This is accomplished y 80 The lines 9, 9 show where the piston should be ranging the v mechanism that i all the when the exhaust valves crack open to be in cylinders the valves open and close at the same symmetry ith th master r d cylinder piston, 85

relative points of their strokes, i. e., the valves in. The distance between t hhes 9, 9 nd 10, 10 the cylinders associated with the articulated rod isa measure .of the lack of phase symmetry of.

V pistons open and close at the same relative pisth valve timing,

ton position, as the 'valves in the cylinder asso- 1 Fig 3 th lines 13, 13, 13 r p t di ciated W e master 1 d D To this end grammaticallythe center lines of the exhaust 90 thfi cam followers are from their normal valve cam ollowers when equally spaced and center lines by such an amount'as will compenwhich equal spacing produces th lack of t sate for the out of phase timing of the valves ing phase symmetry as shown by the lines, 9, 9 Opening and closing o d e pec y and 10, 1o. Ofisetting the cam followers as in- Q 40 fo the t t of e aus valve op i s a d dicated by the dotted center lines, 14, 14 will 95 e valves c g Also the leading d i cause the lines 9, 9 and 10, 10 to coincide and s p t of the 08m p fi e e ap to thus cause the exhaust valves to open at the' ve constant velocity 0! V P 8- Onthe. same relative portion of the stroke in all the xha p ng ilmc ionthis insures that when cylinders. Similarly the closing of the inlet t va ve rac s op n h speed f the as valves in all cylinders ma be regulated as to 0 leased will be of constant velocity'irrespective phase symmetry, of any variation in valve clearancesdue' to un- We have shown in Fig. 4 a method of offsetting equal cylinder expansion, valve gear wear or the cam followers in order to compensate for the neglect f p p r a ju tment. unequal timing occasioned by the use of a mas- On some engines the articulated rod cylinders ter connecting rod and articulated connecting have a slightly different length of stroke as comrods. This illustration is merely one method by pared with that of the master rod cylinders. ,which' the cam followers may be ofiset and many Where this occurs the correction of the valve other methodswill be suggested to thosefamiliar gear is based on the master rod cylinder perwith the art.- In said Fig. 4 we have shown the 5 centage of stroke. Where all cylinders have the cylinders 1, 2, and 3 and have indicated the center lines 13 and 14 as shown in Fig. 3. We have also shown a cam 19 formed with cam lobes 21, 22, 23 and 24. The cam and cam lobes are adapted to contact with rollers 25 rotatably secured to the inner ends of cam followers 26. The cam followers 26 for the cylinder 1, which is associated with the master rod 4, are mounted in guides 27. It is to be noted that the guideway for the followers in the guides 27 are formed concentric with the periphery of said guides. The cam followers 26 for the cylinders 2 and 3 are mounted in guides 28. It is to be noted that the guideway of guides 28 are eccentric with the periphery of said guides and inasmuch as the bores in the crank ease thru which the guides are fitted are positioned 120 apart, the cam followers are necessarily positioned slightly more or less than that distance apart, i. e., they are unequally spaced.

The outer ends of the cam followers 26 are attached to push rods 29 which extend upward thru the push rod housings 30 and are attached at their outer ends to the rocker arms 31 by which the valves 16 are actuated.

Fig. 2 shows the shape of valve cam best adapted to be used with the offset cam followers. The entering and trailing edges 12, 12 are of the constant velocity, zero acceleration type while the main portion, 11, may be of any preferred contour.

It is to be carefully borne in mind that the.

emitted. In 'order that all the exhaust valves ;will open at the same rate, regardless of variations in the individual clearances, the portions 12, 12 of the cams must be of a contour that will impart a constant velocity to the cam follower,

While we have described our invention in detail in its present embodiment, it will be obvious to those skilled in the art after understanding our invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. We aim in the appended claims to cover all such modifications and changes.

What we claim is:

1. In an internal combustion engine, radially arranged equally spaced cylinders, pistons for said cylinders, valves for said cylinders, and means for operating said valves in regular cycles of unequally spaced intervals.

2. In an engine having radially arranged vcylinders, pistons for said cylinders, a crankshaft,

a master rod connecting said crankshaft with one said piston, articulated rods connecting said master rod with the other said pistons, a valve for each cylinder, a cam having a lobe, and cam followers contacting at times with said lobe for operating said valves, said cam followers being so spaced with respect to their respective cylinders as to cause functioning of their respective valves at the same relative position of the piston in each said cylinder.

3. In an engine having radially arranged cylinders, pistons for said cylinders, a crankshaft, a master rod connecting said crankshaft with one said piston, articulated rods connecting said master rod with the other said pistions, a valve for each said cylinder, a plurality of cams, cam followers contacting with said cams for operating said valves, said cams and said cam followers being so spaced with respect to said cylinders as to cause functioning of the valves at the same relative position of the piston in each said cylinder.

4. In an internal combustion engine, a plurality of radially arranged equally spaced cylinders, a crankshaft, pistons in said cylinders, a master rod connected to one of said pistons and to said crankshaft, articulated rods connected to the other said pistons and to said master rod, valves for said cylinders, a cam, lobes on said cam, and cam followers spaced unequal distances apart for coacting with said cam lobes for operating said' valves.

5. -In an internal combustion engine, radially arranged equally spaced cylinders, pistons for said cylinders, a master rod connected to one of said pistons and to said-crankshaft, articulatedrods connected to the other saidpistons and to said master rod, intake and exhaust valves for each of said cylinders, means for opening and closing each of said valves at the same relative positions of the associated piston in each of said cylinders, said last named means comprising a cam, a lobe on said cam, and cam followers certain of which are offset from the center line from the center of the crankshaft to the rocker arm.

6. In an internal combustion engine, radially arranged cylinders, valves for saidcylinders, a cam for operating said valves, a cam follower for coacting with said cam, and a guide for said cam follower, said guide being formed with an eccentric bore.

ARTHUR NUTT. ARTHUR H. LEAK. HARRY L. CHISHOLM, JR. 

